Uptake of Ni(II) from aqueous solution onto graphene oxide: Investigated by batch and modeling techniques

The contamination of Ni(II) on the apple orchards soil is more serious nowadays. The uptake of Ni(II) from aqueous solutions on graphene oxide (GO) was investigated by batch, XPS and modeling techniques. The batch experiments indicated that the uptake of Ni(II) on GO increased significantly with increasing pH from 2.0 to 6.0, and the high-level uptake of Ni(II) was observed at pH > 6.0. No effect of ionic strength on Ni(II) uptake indicated inner-sphere surface complexation dominated the uptake of Ni(II) on GO. The maximum uptake capacity of GO for Ni(II) calculated from Langmuir model was calculated to be 81.97 mg/g at pH 5.0 and 293 K. The results of XPS spectra indicated that a variety of oxygen-containing functional groups were responsible for the uptake of Ni(II) on GO. The uptake process of Ni(II) on GO can be satisfactorily fitted by surface complexation modeling using diffuse layer model with two inner-surface complexes. These findings are crucial for the potential application of graphene oxide in the uptake of heavy metals in environmental cleanup.